In elementary school, I had the best sticker collection. I had big stickers, little stickers, dentist stickers, school stickers, shiny stickers, used stickers, new stickers, animal stickers, sky stickers, and even smelly stickers. I even talked my mom into buying me an album for them. I traded stickers with friends and we perused our collections together.
After a while, I stopped collecting them and the following year when I looked through the collection, it was clearly a bunch of junk. I remember how I felt about the stickers, but that same proud feeling was no longer there. Even the most expensive stickers were easy to give up. I played school with my siblings and neighborhood friends and got rid of all the stickers as I "graded" their papers. Of course, I didn't charge them for them, so the money invested in the collection was solely for my immediate enjoyment. I understand that.
With just a general knowledge of supply and demand, we know that an item is only worth what people are willing to pay for it. So, the well known saying, "One man's trash is another man's treasure," can also go the other way. "One man's treasure is another man's trash."
Here's where collections come into play. When someone has collected an item, no one else is ever going to have the same sentiments about that item as the collector has. So, if you've collected souvenirs from all of your travels, those have value to you. The souvenir serves as a memory of the fun and excitement of that vacation. When you try to give that collection away, nobody will treasure it the way that you did.
A couple of years ago, my neighbor had a garage sale. One of things that they were trying to sell for an outrageous price was a collection of books. Of course they had priceless memories of each of them, but as the day went on, no one was willing to pay the price on the sticker. The collector refused to either break up the collection or come down on the price. Although they were desperate for the space and money made from the collection, they refused to meet the customers' requests and ended up keeping their collection. I say, it was better that way.
No one will care for your collection the way that you will*, so each collection is something personal. And it should stay that way. (*This most often applies to strangers, maybe friends. If you have a collection that your family loves with you, they would probably love a chance to own it.)
Just my opinion. What's yours?